This project is developed in adolescent patients who have need of endodontic treatment in necrotic molars. The patients were randomly divided into two groups of treatment: one and two visits. The treatment protocol is the same for both groups, except the number of visits and the use of intra canal medication in the group treated in two visits. Patients will be followed clinically and radiographically for a minimum period of two years. The data was collected by the evaluation of postoperative pain and to determine the healing of periapical lesions, characterizing the success of the treatment.